Although this is a relatively simple map, you will be dealing with plenty of enemies. From the start, you are supposed to head south, then east to the room below. Take the teleporter to the pit with the yellow key and the rocket launcher. After taking them, backtrack to the start and head to the big room above the pit, fighting enemies as you go. The yellow door on the eastern side has a cyberdemon and some revenants who will teleport behind you. Take them out and hit the switch, which lowers more columns with monsters, as well as the exit, which is close to the starting point.